Efficient SO2 Capture through Multiple Chalcogen Bonds, Sulfur-Centered Hydrogen Bonds and S•••π Interactions: A Computational Study

The non-toxic, environment friendly, biodegradable properties and cost effectiveness of active pharmaceutical ingredients (APIs) allow them to be used as green-solvents for several applications. The presence of multiple binding sites in the APIs has an additional advantage for the flue gas capture. Herein we report a detailed analysis of efficient SO2 capture by the anions associated with APIs through several strong and weak non-covalent interactions. The DFT studies and Langmuir adsorption model suggest that the APIs based anions are highly efficient alternatives for SO2 capture at low as well as high partial pres-sures (0.01-0.1 MPa) of SO2. The absorption capacity can be achieved as much as 5.8 mol SO2/mol APIs; the best absorption capacity till reported. Our computational results suggest that for the efficient SO2 capture, the enthalpy of absorption (Delta H) should be -65 to -50 kJ.mol(-1); below this range absorption capacity reduces drastically. This study also emphasizes the importance of weak interactions (S center dot center dot center dot pi and C-H center dot center dot center dot O and C-H center dot center dot center dot S hydrogen bonds) together with the strong chalcogen bonds to be considered in designing new absorbing materials for SO2 capture.